Electrical wiring device



April 19, 1949. I c, GAYNQR 2,467,820

ELECTRICAL WIRING DEVICE Filed April 18, 1945 Arlhzz t z'aymr WwWn/M ATTORNEY$ Patented 19,1949 I I UNI-TED ELECTRICAL WIRING DEVICE Arthur- C. Gaynor, Stratford, Conn., assignor to- Joseph I". Gaynor, Milford, Conn.

Application April, 1945, Serial No. 539,025

8 Claims. (CL 200-166) la This invention relates to electrical wiring devices, switches, connectors and the like, and more particularly to means for-mounting the contacts and other circuit elements in such devices.

It is common practice in electrical devices to mount circuit elements such as contacts, ter-- minals, etc., on bodies comprising insulating molded pieces or cast pieces by means of screws threaded into metal inserts molded in the pieces.

Various means have been employed to eliminate the necessity of using the threaded inserts, since such arrangement made the molding of the pieces slow and costly. .Where but a limited amount of molding equipment is available, and it is essential that production from the equipment be increased, this elimination of molded-in inserts has provided the answer to the production prob-- lem.- In my copending application, Serial Number 537,521, filed May 26, 1944, entitled Electrical wiring device, now abandoned, I disclose a terminal or contact post having a twopart anchorage adapted to extend into a hole or well in a molded piece, the anchorage having a bowed member which may be straightened by use of a punch to cause-the parts of the anchorage to be spread and to permanently grip the side walls of the well. This arrangement eliminated the necessity of using molded inserts.

Other means directed along similar lines have also been proposed, but in each case the base or anchorage of the contact member was enlarged or spread by use of a punch which straightened a bowed spreader plate or strip. After the contact member was thus secured in the molded piece, the terminal or binding screw was threaded in place, the assembly being then ready for the wiring.

In these prior proposals two operations were generally involved, the punch operation wherein the contact member is secured to the casing of b the device, and the operation of threading in the whereby the operation of threading in the terminal or binding screw is utilized to operate an anchorage'so that the contact member is firmly secured in place on the supporting body, and at the same time the screw is positioned and placed in readiness for the wiring of the device.

Thus a saving of time is effected in the fabrication of the device by the elimination of the punching operation, and where a number of contacts or terminals are used in each device, this saving may become a sizeable factor.

In addition, the structure of the contact and anchorage unit of the invention is extremely simple and economical to fabricate, yet the fastening or retention provided is firm and secure, so that additional savings .are efiected without sacrificing quality.

In accomplishing these objects the invention provides an anchorage structure in the form of a threaded split sleeve adapted to be slidably received in a recess or well of the supporting body, and adapted to receive in its bore a standard binding or terminal screw. The threads of the sleeve are slightly under standard size, and after insertion of the sleeve in the recess the threadingin of the terminal screw causes the sleeve to spread, and to grip the walls of the recess, thereby securely anchoring the contact member. I have found that the sleeve may be formed of a ductile material so that threading-in of the screw will permanently spread the sleeve, and that. when the screw is backed ofiafter being driven home, the sleeve if it has a comparatively heavy wall will remain sufliciently permanently spread to maintain a firm anchorage. Also, there is but little tendency toward binding of the screw after it has been backed off slightly. Instead, the screw may be readily turned with either the fingers or a screw driver.

When the screw is again tightened for purposes I of binding a wire, the screw threads will be continually exerting a further spreading force on the sleeve due to the angularity of the engaging thread surfaces, thus assuring a permanent anchorage when the device is in use.

In the broader aspects of the invention the sleeve may have any shape desired, cylindrical, square, etc., although at present it is preferred to make the sleeve cylindrical.

For purposes of illustration the anchorage structures and contacts supported thereby are shown in connection with an electric switch. However, the present invention has utility when applied to electric plugs, connectors, relays, and other wiring devices, as well.

Other features and advantages will hereinafter appear.

In the accompanying drawings:

Figure 1 is a longitudinal section taken through the center line of the switch embodying the invention, showing the two halves of the casing, and the parts carried thereby, separated.

Fig. 2 is a plan view of the casing half which carries the switch contacts and improved mountings therefor.

Fig. 3 is a fragmentary plan view of the righthand end of the casing half of Fig. 2, showing one switch contact after being placed in position and prior to its being fastened or secured, and

Fig. 4 is a perspective view of the switch contact and anchorage means of Fig. 3.

As shown in Figs. 1 and 2, the switch embodying the invention has an elongate molded casing it formed of two separable halves II and II, the latter carryin parts of the switch mechanism and, when assembled, being fastened together by screws and nuts ii.

A pivoted switch blade i4 and operating mechanism i5 therefor are mounted on the part II of the casing, the operating mechanism including a toggle Ii and finger-operable lever ll, all as fully described in my Patent No. 1,966,091, issued July '10, 1934, entitled Electric switch."

The blade ll cooperates, to control a circuit, with a pair of knife contacts i8 and I! carried by the part I! of the casing. When the blade I4 is in the position shown in Fi 1 and the switch is assembled, the contacts i8 and I9 will be bridged, this constitutin the closed-circuit position of the switch. If, when the switch is in this position, the finger-operable lever I1 is depressed, the switch blade ll will be caused to snap to an opposite position wherein it does not engage the contacts [8 and IS, the switch then being open-circuited.

According to this invention the contacts i8 and I! are provided with novel, extremely compact supporting and connecting means whereby, prior to the wiring of the switch, the contacts may be securely permanently mounted on the part I! of the casing as a result of threading-in of the contact binding screws, without the necessity of the casing having molded-in inserts or studs, or threaded or undercut walls. The arrangement provided is such that the positioning and fastening of the contacts is accomplished in an extremely simple manner, with a minimum of time and inconvenience. Moreover, the procedure for installing the contacts in the casing does not require special tools such as punches, or any separate operations in addition to the necessary operation of inserting and placing the contact binding screws.

When installin the contacts, the mounting means therefor are merely placed in recesses in the casing, and the contact binding screws driven into threaded apertures in the mountings, thereby causing the latter to be deformed and frictionally seized and retained by the walls of the recesses.

Referring particularly to the contact i9. this may comprise part of a unit formed, as shown in Fig. 4, from flat strip stock such as brass or bronze, the contact having integral therewith and extending substantially at right angles therefrom a supporting arm lta curled at its end into an eye iOb which latter forms the anchorage of the unit. The eye I 8b is tapped so that it may receive a binding screw, the internal threads formed by the tapping having a size sliBhtly smaller in diameter than the sire of standard screws, such as the binding screws 20 shown in Fig. l.

For receiving the arm Ila and eye lab associated with the contact II, the part I! of the casing is provided with a circular recess 2| and a juxtaposed elongate recess 22 which latter opens into the recess ii. The shape and size of these recesses is such that the arm Ila and eye l9b may be dropped or easily pressed in place in them as shown in Fig. 3. After this has been done, one of the binding screws 2| is threaded fully into the eye lib, causing a spreadin of the latter, due to the difference in the thread sizes, as shown in Fig. 2, and causing the eye to be frictionally seized and held by the walls of the recess 2|.

To accomplish this seizure, the thickness of the strip comprising the eye llb, and the size of the thread tapped into the eye are so proportioned with respect to the size of the aperture II that when the standard binding screw 20 is threaded into the eye it will enlarge the same sufllciently to cause the desired firm seizure.

Preferably the material comprising the eye lSb is ductile enough to permit it to be readily permanently expanded by insertion of the screw 2|, while still retaining considerable strength in the tapped threads I9c.

In the broader aspects of the invention the metal strip forming the eyes ilb and Ilb need not be so ductile that the eyes are permanently deformed or spread when the screws have been completely threaded-in, Instead, if the eyes have a certain amount of resiliency so that they tend to return to their original smaller diameter when the screws are removed again, the device will still have utility. Ordinarily the binding screws 2| are not removed from the eyes when securing conductors to the latter. However, if they should be removed, after their reinsertlon the downward pressure on their heads due to driving them in with a screw driver will cause the eyes to be properly seated, and as the screws are pulled up tight the radial component of the force exerted on the internal threads of the eyes will spread the latter and hold them securely in the casing.

I have found that, due to the ductility of the material comprising the eye [9b, after the screw 20 has been completely threaded into the eye and backed off a slight amount, it will turn comparatively freely, so that the fingers or a small screw driver may be used to further loosen it. Also, even though the screw 20 is completely removed from the eye IBb after having spread the latter, the seizure of the eye by the walls-of the recess 2! is maintained so that the contact I9 is rigidly held in its adjusted position and may not be withdrawn except through the use of considerable force. Therefore, after the screw 20 has been initially driven in to its full depth I prefer to immediately back it off slightly, whereupon the contact is in readiness for connection to a conductor.

Considering this latter operation, if the screw 20 must be removed entirely this may therefore be readily done without much effort or loss of time, due to the ease with which the partially backed of! screw may be turned. In most instances, however, the wiring may be placed under the head ofthe-screw while it isbelng-supported in the eye I 917, only partially backed om. In a similar manner the contact it maybe formed from a flat metal strip, integralwith a supporting arm Ila which latter terminates in a curled end or eye Ilb for frictional seizure in a recess 23 upon threading in a binding screw 20.

Preferably the strip material from which thecontacts i8, i9 and associated mountingmeans are made is of suiilcient thickness to provide a circular face of fairly substantial area'when'the eyes are formed, such as the face 19d of the eye .llb.1'I-'he face I911 may thus cooperate'with the head of the binding screw 20 so that a wire or other conductor may be readily clampedbetween these cooperating parts.

Referring to Fig. 1 the shanks of the binding screws 20 are shown as being smooth andunthreaded immediately adjacent the heads thereof. This construction is incidental to the fabrication of the screws, and I have found that it may aid in spreading the eyes I81) and Nb of the contacts when the screws are driven in fully. However, it is not necessary for the screws to have smooth shank portions to properly spread the eyes, since the spreading may be accomplished by the threads of the screws. No difficulty is encountered in starting the screws, since the tips of the screw shanks are normally slightly tapered, or smaller in diameter than the main portions of the shanks. Therefore the tips may readily be started in the eyes IBD and It").

It will thus be seen that the present invention provides an extremely compact, simple and effective anchorage for contacts, circuit elements and the like, which is made to function merely in response to the necessary operation of threading-in the binding screw, and therefore does not require a separate operation to accomplish the anchoring. A considerable saving of time is thereby effected. The anchorage thus obtained is firm and secure for all-practical purposes of the device, and does not interfere withthe securing of wiring to the contacts. Also it is extremely compact and economical-to produce; I v v As a result of the improved mounting and connecting means provided by the invention the parts split internally-threaded sleeve extending into the be. permanently frictionally seized by-the said 're-' c'ess wall, the head of the screw being adapted tocooperate with the exposed end-portion of v and; expand the same, .therebyto cause the'walls of the recess to frictionally hold the sleeve and contact.

a. Inan electrical wiring device, a body having a'recss: an electrical conductin element comprising a flat strip bent at one endinto an expansible split cylindrical sleeve, said sleeve being internally threaded and extending into the recess for engagement with the walls thereof; and a binding screw threaded into the sleeve for making an electrical connection to said, element, said screw being of a size to expand the sleeve and cause the latter to be frictionally held by the recess walls.

5. In an electrical wiring device, acasing having a pair of juxtaposed recesses opening into each other; a current conducting element including an expansible body and an armextending therefrom and connecting the body to the element, said arm and body being located; respectively in the said recesses, the body having internal threads and being adapted to expand against the walls of the associated recess for frictional seizure thereby when an expanding force is exerted against said threads; and a binding screw for threading into the saidbody to clamp a conductor against the same to form an electrical connection thereto, said screw when threaded intothe body expanding the latter so u that it is frictionally held by the casing.

6. In an electrical wiring device, a casing having a pair of juxtaposed recesses'opening into each other; acircuit element comprising a length of fiat 'metal strip having one end formed into an eye and threaded internally, said eye and the remainder of the strip being located in the said recesses respectively, and the eye being adapted to expand against the walls of its associated recess for frictional seizure thereby when an expanding force is exerted against said threads; and a binding screw for threading into the said eye to clamp a conductor against'the same, said screw expanding the eye into engagement with the walls of the recess so that it is frictionally retained by the casing.

"I. In an electrical wiring device, a casing having a pair of juxtaposed recesses opening into each other; an electrical contact element comprising a length of flat ductile metal strip having one end formed into an eye and threaded internally, said eye and the remainderfoi the strip being recess for engaging a wall thereof; and a binding screw adapted to thread 'intothe sleeve to, con-1 nect a conductor thereto'and to spread the sleeve and cause the same to be frictionally seized'by the'said recess wall.

2. In an electrical wiring device, a bodyv having force is exerted against said threads; and a bindeye being adapted to be expanded permanently against the walls of its associated recess for afrecess; a'split internally-threaded sleeve i'extending, into therecess for engaging a wall ther'eo and having a tangentially disposed contact-pro] jecting therefrom. said sleeve having an exposed" 1 end portion adapted for engagement with-.aacom' ductor; and a binding screw for threading-into.

the sleeve, said screw'being of a size-to perma' located in the said recessesrespectively, and the frictional seizure thereby when an expanding ing screw for threading into the said eye to clamp a conductor against the .same, said screw per- 1 manently expanding the eye so that the contact v strip is frictionally'retained by the casing.

8. In an electrical switch, a supporting body of [molded insulating material; a movable switch blade and means for operating same, supported on the body; a stationary contact cooperating with the switch blade, said body having a recess molded therein and said contact having one end formed into an expansible eye extending into the recess for engagement with the walls thereof, the eye having internal threads and being adapted to expand against the recess walls for frictional seizure thereby when pressure is exerted on said threads to hold the contact against movement by the switch blade; and a screw for threading into the eye to expand the latter and thereby secure the same to the molded body.

ARTHUR C. GAYNOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Number 

